1. Field of the Invention
The present invention relates to a method of treating waste liquors containing large amount of phenol.
The present invention further relates to a method of treating waste liquors containing methanol and formaldehyde in addition to phenol.
2. Description of the Prior Art
Usually, waste liquors discharged from phenol production industry, phenol resin or its derivative production industry, petroleum-refining industry, coal gas production industry, coke production industry, hospitals, experiment stations, laboratories and the like contain high concentration of phenols such as phenol, cresol, catechol and their derivatives. From an aspect of environmental sanitation, many towns and cities have nowadays acts or regulations to obligate ones to remove phenols for preventing environmental pollution.
The term "phenol" or "phenols" used herein means a compound or compounds selected from the group consisting of phenol, o-, m- and p-cresol, saligenine, o-, m- and p-hydroxybenzaldehyde, salicylic acid, catechol, 3-methylcatechol and 4-methylcatechol, etc.
Heretofore, in order to remove phenol from a waste liquor containing phenol, there have been proposed many methods such as solvent extraction method, activated carbon adhesion method, chemical oxidation method, incineration method, activated sludge method, etc. Though all the methods attain average level of effects, they have several problems when the amount of influent waste liquor to be treated fluctuates considerably and the waste liquor contains a high concentration such as 800-1200 ppm of phenol. The problems are illustrated as follows.
(1) In solvent extraction method, solvent is very expensive, so that operation is difficult. PA1 (2) In activated carbon adhesion method, adhesion capacity of the activated carbon decreases rapidly. Namely, consumption of the activated carbon is very large, so that control and maintenance of this method are difficult. PA1 (3) In chemical oxidation method, running cost is considerably large for the sake of oxidizing agents such as H.sub.2 O.sub.2, O.sub.3, etc. PA1 (4) In incineration method, running cost is extremely large owing to combustion fuel. PA1 (5) In activated sludge method, it is rather difficult to maintain the activity of acclimated microorganisms, which is weak against fluctuation in phenol concentration of an influent waste liquor to be treated. Besides, dilution of the waste liquor is essential, so that apparatus used in this method become necessarily large. Therefore, investment cost is quite expensive. PA1 (6) In conventional activated sludge method, CN and SCN ions existing in an influent waste liquor discharged from coal gas production industry or coke production industry have to be treated or removed preliminarily.
Additionally, there are hitherto waste liquors containing high concentrations of methanol and formaldehyde in addition to phenol, such as waste liquors from phenol resin production industry etc. The three compounds have large toxicities adversely influencing upon a biological treatment of the waste liquors. For this reason, heretofore, waste liquors can be treated by activated sludge method only after dilution with a large amount of water or a complicated physical and chemical pretreatment for decreasing the toxicities of the three compounds, as described in Japanese patent application laid-open No. 62,659/79. However, the activated sludge method has disadvantages that the usage of a large amount of water for dilution results in not only extremely large amount of diluted waste liquor to be treated, but also considerably large expenditure of the water for dilution, and that the physical and chemical pretreatment necessiatates a large amount of chemicals, labor, time and a large scale of apparatus.